Add resources for datastructures

[g-savitha]

Online platforms:
1.Codechef
2.Codeforces
3.LeetCode
4. GeeksforGeeks
5.Hackerrank
6. Hackerearth
7. TopCoder
8. SPOj
9.Codewars
10.CommonLounge
11.UVa Online Judge
12.Interviewbit

Books:
1.CLRS
2. Competetive programming by Felix and Steven Halim
3. Algorithm design by Kleinberg Tardos
4. Cracking the coding interview - Gayle McDowell
5. Datastructures and algorithms made easy series - Narasimha karumanchi

Free Courses

1. mycodeschool
2. mit opencourseware
3. algorithms 1,2 in coursera

Paid courses
Interview prep- Ravindrababu ravula

[g-savitha]

@duttakapil

[duttakapil]

@savitha-gollamudi sorry for looking at this so late. Would it be possible for you to send a Pull Request to the repo with these resources, and also link them? Also do make sure to format them properly. Will merge the PR when you send it